1. Field of the Invention
The invention relates to a device for influencing the air flow in the area of the roof opening of an openable motor vehicle roof with at least one wind deflector which is vertically displaceable in the area of the front edge of the roof opening between a neutral position in which the top of the wind deflector does not project above the fixed roof surface, and an extended position in which the top of the wind deflector does project above the fixed roof surface.
2. Description of Related Art
Devices of the initially mentioned type are currently being used in most vehicles with an openable roof. In such cases, the wind deflector is used primarily to deflect the air flow which streams over the motor vehicle roof during driving of the vehicle, such that the wind noise which arises when driving with the motor vehicle roof opened is reduced.
In particular, in motor vehicles with a roof opening which can be closed by means of a sliding or sliding/lifting cover, it has been shown that, especially for covers which are opened wide or completely, low frequency air vibrations are formed when opened. At certain motor vehicle speeds, the vehicle interior acts as a resonator so that air vibrations with considerable intensity can develop and they are generally perceived as very disturbing; the term xe2x80x9crumblingxe2x80x9d of a sliding roof has been coined for it by specialists.
It has been found that rumbling can be at least reduced by provisions being made for swirling the air flow streaming over th e motor vehicle roof For this reason, published German Patent Application DE 195 18 696 discloses a wind deflector which is made to be raisable in the area of the front edge of the roof opening and which is provided with an air permeable net which is in its lower area in the raised position. In this way, the air flow streaming over the motor vehicle roof in vehicle operation is broken down into a portion flowing over the top edge of the wind deflector and a portion flowing through the net under the wind deflector. As a result, a boundary layer is formed between the air which is essentially at rest in the vehicle interior and the air flowing at high speed over the roof opening and beyond, and thus, the rumbling will be reduced.
However, as mentioned initially, rumbling appears disruptive only in a certain range of vehicle speeds. However, this technique would be disruptive to attainment of a wind deflector device which is optimized outside of this speed range for reducing the xe2x80x9cnormalxe2x80x9d wind noise since this cannot be done with the wind deflector of German Patent Application DE 195 18 696 since, in every operating position of the wind deflector, a partial flow streams under the wind deflector.
Accordingly, an object of this invention is to devise a device for influencing the air flow in the area of the roof opening of an openable motor vehicle roof by means of which both largely optimum reduction or prevention of driving noise as well as largely optimum reduction or prevention of rumbling can be achieved.
This object is achieved in a device of the initially mentioned type by its being possible to move the wind deflector selectively into at least a first extended position in which an air flow streaming over the motor vehicle roof is routed exclusively over the top of the wind deflector, and into at least a second extended position in which an air flow streaming over the motor vehicle roof is routed at least partially under the wind deflector.
Thus, in the proposed device, the wind deflector can be moved, depending on the desired effect, either into the first extended position in which it is used to reduce the xe2x80x9cnormalxe2x80x9d flow noise in the motor vehicle interior, or into a second extended position in which rumbling is prevented or at least attenuated. Preferably, the arrangement is made such that there are several first and second extended positions, especially such that the wind deflector can be adjusted continuously between the neutral position and the position of its maximum raised height.
In particular there can be an actuating arrangement for moving the wind deflector, which can comprise especially an electric motor. Here, the actuator preferably has an electronic control arrangement for triggering the electric motor depending on preadjusted or freely selectable parameters. The actuating parameters are especially the vehicle speed and the degree of roof opening, for which reason, according to one preferred embodiment of the invention, there can be sensor technology coupled to the electronic control arrangement for acquiring the motor vehicle speed and/or the degree of roof opening. The adjustment of the vertical position of the wind deflector can thus take place automatically, for example, by assigning a certain vertical position of the wind deflector to certain vehicle speed ranges depending on the degree of roof opening.
According to a preferred embodiment, between the front edge of the roof opening and the wind deflector, there is a sealing arrangement which can be joined to the wind deflector and which, in the first extended position of the wind deflector, prevents an air flow from streaming through over the motor vehicle roof under the wind deflector. Preferably, on the front edge of the roof opening, there is an essentially vertically aligned sealing surface which is assigned to the sealing arrangement. In doing so, the sealing arrangement prevents the air flowing over the motor vehicle roof under the wind deflector from flowing through over the entire engagement area of the sealing arrangement with the vertically aligned sealing surface, so that while maintaining this sealing function, the wind deflector can assume several different vertical positions, by which the reduction of wind noise can be optimized depending on, for example, the motor vehicle speed.
In another embodiment of the invention, the wind deflector can be provided with openings which, in the second extended position of the wind deflector, enable air to flow through over the motor vehicle roof under the wind deflector. In particular, the wind deflector can have opening gaps in the area between its lower edge and the sealing arrangement. By means of these openings or opening gaps, air flowing through under the wind deflector can be additionally swirled, by which the rumbling is reduced even more effectively.
The device in accordance with the invention for influencing the air flow in the area of the roof opening of an openable motor vehicle roof can be integrated into a motor vehicle roof which, in the area of the front edge of the roof opening, has a frame component such that the wind deflector, in its neutral position, is held at least partially in the frame component. Here, the configuration can be such that the wind deflector is arranged in its neutral position so that it can be lowered to under a closing element which is provided for closing and at least partially exposing the roof opening.
The invention is explained below with reference to the drawings which show by way of example, multiple embodiments of the invention.